Practice Essentials
Thoracic injuries account for 20-25% of deaths due to trauma and contribute to 25-50% of the remaining deaths. Approximately 16,000 deaths per year in the United States alone are attributable to chest trauma. [1] Therefore, thoracic injuries are a contributing factor in as many as 75% of all trauma-related deaths. Any organ within the chest is potentially susceptible to penetrating trauma, and each should be considered in the evaluation of a patient with thoracic injury.
The increased prevalence of penetrating chest injury (associated with the "drug war" in the United States) and improved prehospital and perioperative care have resulted in an increasing number of critically injured but potentially salvageable patients presenting to trauma centers. [2] The classic "trimodal" temporal distribution of trauma deaths has been questioned, even though it has been widely taught in the design of trauma systems. [3]
Current management of penetrating chest trauma (PCT) is a hurried, brute-force approach necessitated by the life-threatening nature of many of these injuries. As surgical experience with less invasive techniques and minimal incision approaches increases, these methods will likely find their appropriate places in the treatment of these patients. At present, however, traditional approaches and techniques predominate in the treatment of critically injured and frequently unstable patients.
Anatomy
The anatomy of the thoracic cage is well known and encompasses the area beneath the clavicles and superior to the diaphragm, bound laterally by the rib cage, anteriorly by the sternum and ribs, and posteriorly by the rib and vertebral bodies. The thorax may be entered via three main approaches, as follows:
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Sternotomy
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Thoracotomy (incising between selected ribs, most commonly the fourth and fifth) on either the right or left side
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Clamshell incision, consisting of left and right thoracotomy incisions traversing the sternum to join the two
Additional modifications of each of these approaches exist but are not discussed in detail here.
Particular care must be exercised laterally near the sternum, where the internal thoracic (mammary) artery lies 2-4 cm on either side. Similarly, it must be remembered that immediately inferior to each rib body are the intercostal artery, vein, and nerve, from which voluminous bleeding can occur. Patients have required reexploration for injuries to these various vessels and have exsanguinated as a result of missed injuries to these structures.
Anteriorly, injuries to the heart should be presumed to have occurred if entry points are present anywhere between the two midclavicular lines. On occasion, significant injury to the heart has occurred from entry points lateral to these margins, as in gunshot or missile injuries.
Exceptionally long penetrating instruments and weapons (eg, arrows, swords, or lances) can also directly penetrate the heart from a distant entry point. Similarly, injuries to any of the intrathoracic structures can be effected with long penetrating devices; accordingly, the possibility of injuries to the diaphragm, great vessels, or posterior mediastinal structures must be considered in these cases.
The right atrium and right ventricle are the anterior portions of the heart; these areas are the primary sites involved in penetrating injuries of the heart.
Pathophysiology
As noted by Inci et al in a 1998 study of 755 patients with thoracic injuries, PCT comprises a broad spectrum of injuries and severity. [7] The injuries and the number of patients (some with more than one injury) in this study were as follows:
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Hemothorax - 190
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Hemopneumothorax - 184
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Pneumothorax - 144
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Diaphragmatic rupture - 121
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Open hemopneumothorax - 95
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Pulmonary contusion - 50
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Open pneumothorax - 24
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Rib fracture - Fewer than 2 fractures, 16; more than 2 fractures, 13
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Subcutaneous emphysema - 14
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Bilateral pneumothorax - 9
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Open bilateral hemopneumothorax - 13
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Pneumomediastinum - 6
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Thoracic wall lacerations - 4
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Bilateral hemopneumothorax - 3
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Open bilateral pneumothorax - 3
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Sternal fracture - 3
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Bilateral diaphragmatic rupture - 2
The clinical consequences depend on the mechanism of the injury, the location of the injury, associated injuries, and underlying illnesses. Organs at risk, in addition to the intrathoracic contents, include the intraperitoneal viscera, the retroperitoneal space, and the neck.
Etiology
Mechanism of injury
The mechanism of injury may be categorized as low-, medium-, or high-velocity, as follows:
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Low-velocity injuries include impalement (eg, knife wounds), which disrupts only the structures penetrated
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Medium-velocity injuries include bullet wounds from most types of handguns and air-powered pellet guns and are characterized by much less primary tissue destruction than wounds caused by high-velocity forces
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High-velocity injuries include bullet wounds caused by rifles and wounds resulting from military weapons
Shotgun injuries, despite being caused by medium-velocity projectiles, are sometimes included within management discussions for high-velocity projectile injuries. This inclusion is reasonable because of the kinetic energy transmitted to the surrounding tissue and subsequent cavitation, as described by the following equation:
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KE = ½mv2
where KE is kinetic energy, m is mass, and v is velocity.
Ballistics may be divided into three major categories, as follows:
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Internal ballistics describes the characteristics of the projectile within the gun barrel
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External ballistics examines the factors that affect the projectile during its path to the target, including wind resistance and gravity
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Terminal ballistics evaluates the projectile as it strikes its target
The amount of tissue damage is directly related to the amount of energy exchange between the penetrating object and the body part. The density of the tissue involved and the frontal area of the penetrating object are the important factors determining the rate of energy loss.
The energy exchange produces a permanent cavity inside the tissue. Part of this cavity is a result of the crushing of the tissue as the projectile passes through. The expansion of the tissue particles away from the pathway of the bullet creates a temporary cavity. Because this cavity is temporary, one must realize that it was once present in order to understand the full extent of injury.
Penetrations from blast fragments or from fragmentation weapons can be particularly destructive because of their extremely high velocities. Weapons designed specifically for antipersonnel effects (eg, mines and grenades) can generate fragments with initial velocities of 4500 ft/s, a far greater speed than even most rifle bullets. The tremendous energy imparted to tissue from fragments with such velocity causes extensive disruptive and thermal tissue damage.
Weaponry of the 21st century consists mostly of improvised explosive devices (IEDs). These devices are homemade bombs, and they create a deadly triad of penetrating, blast, and burn wounds. Of the thoracic trauma that is seen in the current Global War on Terror, 40% is penetrating chest trauma.
Prognosis
The outcomes of treating patients with PCT are directly related to the extent of their injuries and the timeliness with which treatment is initiated. Patients arriving in a stable condition may expect full recovery, but those presenting with lesser levels of stability have diminishing probabilities of survival. No attempt should be made to resuscitate, let alone definitively treat, patients presenting with no vital signs or with obviously nonsurvivable injuries (eg, massive cardiac destruction).
Guidelines for initiation of emergency department (ED) thoracotomy (EDT) were published in 2014 by the American College of Surgeons (ACS), the American College of Emergency Physicians (ACEP), the National Association of EMS Physicians (NAEMSP), and the American Academy of Pediatrics (AAP) [8] ; the Eastern Association for the Surgery of Trauma (EAST) published its own guideline in 2015 (see Guidelines). [9]
In a 2010 report from a single center that included 158 patients who underwent thoracotomy within 24 hours after PCT, those patients who died had a significantly lower systolic blood pressure (42 ± 36 mm Hg) than those who survived (83 ± 27 mm Hg). [10]
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Upright posteroanterior chest radiograph of patient with right-side hemothorax.
